(a) Field of the Invention
The present invention relates to a paper feeding mechanism for use with the printer and more particularly, it relates to a paper feeding mechanism capable of opening and closing those tractors through which a sheet of paper is conveyed.
(b) Prior Art
FIGS. 3(A) and 3(B) show one of the conventional paper feeding mechanisms. Driven and support shafts 2 and 3 supported by both side plates of the printer are arranged adjacent and horizontal to a platen 1 of the printer and also parallel to the axial direction of the platen 1 in such a way that the driven shaft 2 is centrally positioned between the platen 1 and the support shaft 3. The driven shaft 2 is driven and rotated by a drive gear (not shown) and swung clockwise by about 100 degrees round the support shaft 3 from the closed state shown in FIG. 3(B) to the opened state shown in FIG. 3(A).
A pair of tractors 4 which are engaged with holes (not shown) on both sides of a sheet of paper S to convey the paper S are supported on the driven and support shafts 2 and 3. Each of the tractors 4 has a drive pulley 5 fitted onto the driven shaft 2, a follower pulley 6 fitted onto the support shaft 3, and a belt 7 stretched between the drive and follower pulleys 5 and 6. Plural pins 8 which have same pitch as that of the paper feeding holes are projected from the outer circumferential face of the belt 7. A pair of paper holder members 9A and 9B which are separated in the vertical direction are swingably supported by the frame (not shown).
When the paper S is to be mounted on the tractors 4, each of the tractors 4 is swung round the support shaft 3 to move from its closed position to its opened position shown in FIG. 3(A). When the paper S stacked is pulled out and its foremost end reaches near the lower paper holder members 9B, as shown in FIG. 3(A), the paper holder members 9B are swung open, allowing the pins 8 on the belts 7 to be fitted into the holes on both sides of the paper S. The paper holder members 9B are then again swung close and, holding the paper S fitted on the belts 7, the tractors 4 are swung anti-clockwise round the support shaft 3 to move from their state shown in FIG. 3(A) to their closed state. The driven shaft 2 is then driven and rotated to feed the paper S. When the paper S passes round the platen 1 and again reaches the tractors 4, the upper paper holder members 9A are swung open, allowing the holes on both sides of the paper S to be fitted onto the pins 8 on the belts 7, and then again swung close. The mounting of the paper S is thus completed, as shown in FIG. 3(B).
In the case of the above-described conventional paper feeding mechanism, however, the drive gear (not shown) which drove and rotated the driven shaft 2 was released from a transmission gear (not shown) which transmitted the drive of a drive source to the drive gear and the follower pulley 6 fitted onto the support shaft 3 was left freely rotatable, when the tractors 4 were under their open state, as shown in FIG. 3(A). The belts 7 were thus allowed to freely run when the tractors 4 were under their open state, thereby making it difficult to fit the holes of the paper S onto the pins of the belts 7. The mounting of the paper S was thus made troublesome and unstable.